Hydraulic stroke regulator for pumps



Allg. 22, 1933. A E| |5 HYRAULC STROKE REGULATOR FOR PUMPS 5sheaves-sheetv 1 Filed Juiy 17, 193'1 IVENTOR A /TfU/P L ELL/5 BY lATTORNEYS( Aug. 22, 1933. A. l.. ELLIS 1,923,923

f HYDRAULIC STROKE REGULATOR FoR PUMPS Filed July-17, 1931 5sheets-sheet 2 ATTORNEYS ug- 22, 1933- A. L. ELLIS HYDRAULIC STROKEREGULATO/R FOR PUMPS` v 5 Sheeis-Sheet 3 Filed July 1.1. 1951V wf L .IVENTOR ART/Juf? L ELL/5 ATTORNEYS Aug. 22, 1933. A. L. ELLIS 4HYDRAULIC STROKE REGULATOR FOR PUMPS ,Filed July 17, 1931 5 sheets-sheet4 INVENTOR ARTHUR l. ELL/5 a *nf/M( ATToRNEtS NWN www hwk U Mmmm@ m Aug.22, 1933. A. l.. ELLIS HYDRAULIC STROKE REGULATOR FOR PUMPS '5Sheets-Sheet 5 Filed July 17, 1951 .Sv ,L s RL Y mE m mL v mW Km TY. v.Mexm 3 U 9 W Fmi- Patented Aug. 22, 1933\ HYDRAULIC STROKE REGULATORFOR PUMPS Arthur L. Ellis, New Rochelle, N. Y., assignor to TheWaterbury Tool Company, Waterbury, Conn., a Corporation of ConnecticutApplication July` 17, 1931. Serial No. 551,386

3 Claims.

The invention relates to hydraulic transmissions of the type whichinclude a hydraulic pump,

and has for its object to provide a novel and is a detail side elevationthereof, with parts in section, on an enlarged scale; Fig. 3 is acorresponding view of a check valve forming part thereof; Fig. 4 is adetail sectional view showing a shuttle valve anda by-pass relief valvevwhich constitute part of the invention; Fig. 5 is a fragmentaryelevation showing another arrangement of the novel features; Fig. 6 is adiagrammatic view thereof; Fig. '7 is a detail vview of a four-way valveincluded in the arrangement, and Fig. 8 is an elevation partly insection of a preferred form of hydraulic pump comprising part oftheconstruction.

For the purpose of illustration and description the invention is shownin the drawings `as embodied in a machine tool of the planer type, itbeing understood that the illustrated example does not define the limitsof the invention, and that is intended to exemplify the general type ofmachine tools for which the novel mechanism is specially designed. Y Inthe drawings 15 represents the reciprocating table of a 'machine tool ofthe planer type, arranged to be -reciprocated by hydraulic means,constituting a hydraulic motor which in the illustrated example isshown'in the form of a cylinder 16 and co-operating elements; in theinstant arrangement the table 15 is carried by the 'cylinder 16, thelatter being slid- 451 ably mounted upon a stationary piston whichdivides' said cylinder 16 into independent, opposite end chambers in anycustomary manner. The aforesaid piston is xed in place by means ofpiston rods 20 and 21 which project in opposite directions beyond thecylinder 16 and are secured in members 22 projecting upwardly from abase 23 constituting part of the frame orsupport of a machine tool ofthe conventional planer type. 'I he piston rods 20 and 21 are hollow andare provided respectively with axial (Cl. 10S-38) channels having nocommunication with each other and terminating at the outer ends of thepiston rods 20 and 2l, said channels being connected with the operatingmechanism as will be pointed out more fully hereinafter. planer or itsequivalent as exemplified by the table 15 may include any and allfeatures commonly found in such tools, and said planer has been shownonly in a fragmentary way because per se it forms no part of theinvention.

The channel of the piston rod 20 is connected with a pipe'28 which leadsto the chamber 29 of a shuttle valve 30, said chamber 29, in turn, beingconnected by means of a pipe 31 with one The side of a hydraulic pump32; thev channel of the 7,0

piston rod 21 is connected by means of a pipe 33 and branch pipe 33awith a second chamber 29a of said shuttle valve 30, said chamber 29abeing in turn connected, by means of a pipe 34, with the other side ofsaid hydraulic pump 32. In the preferred construction a back pressurevalve of suitable form, is located at a convenient pointv between theshuttle valve 30 and the channel of the piston rod 21 in communicationwith thepipe 33'and branch pipe 33a; in addition, a by-pass valve 36,the specific construction of which will be fully described later on, isconnected with the pipes 31 and 34 so as to establish communicationtherebetween under the conditions and in a manner which will appear morefully hereinafter.

As shown in Fig.4 communication between the chambers 29 and 29a of theshuttle valve 30 is controlled by valves 37 and 37a and co-operatingvalve seats 38 and 38a formed at opposite ends of a cage 39 locatedinteriorly of said valve 30 90- 40 or in other words with the valves 3,7and 37a 100 respectively. The plungers 41 are slidably mounted incylinders or recesses 43 formed in the opposite end members 44 oftheshuttle valve 30 and connected by means of passages 45 with the vinteriors of. the chambers 29 and 29a respectively; the plungersv 41partake of the movements of the valves 37 and 37a, and with thecylinders 43 constitute dash pots as will be readily lunderstood. Theinterior passage in the casing of the' .shuttle valve B0 is connected bymeans of a pipe addition to their other functions,

46 with a conventionall expansion box or other storage of oil; as theexpansion box or equivalent storage of oil per se forms no part of theinstant invention and is well known it has not been deemed necessary toshow the same in the drawmgs.

The by-pass valve 36, as also illustrated in Fig. 4, comprises a reliefvalve 47 preferably provided with a peripheral lip 48 for assisting saidvalve to open and to remain open, and co-operating with a valve seat 49formed at one end of a cage 50 secured in the valve casing preferably soas to be removable therefrom. The valve 47 is maintained upon andreturned to the seat 49 by means of a spring 5l, one end of which bearsagainst a member 52 provided with ,a projection 53 in engagement withsaid valve 47; the member 52 is carried by a plunger 54 slidably mountedin a sleeve 55 having an annular dange 56 at its one end against whichthe other end oi said spring 5l abuts. The plunger 54 and sleeve 55, inconstitute means for guiding the member 52 in its movements, said sleeve55 being adjustable by means of an adjusting screw 57 to vary the'tension of the spring 51; the adjusting screw 57 is :dried againstunintentional movement for instance, by means of a lock nut 58; tofurther guard against interference with the screw 57 a protecting cover57a may be screwed into the valve casing to completely enclose saidscrew 57. To steady the valve 47 in its movements and to preventchattering thereof, the one end oi the cage 50 is formed as a cylinder59 which communicates with the interior of the casing oi the valve 36and slidably accommodates a plunger 60 connected by means of a stem 61with the valve 47; the plunger 60 and cylinder 59 together constitute adash-pot as clearly shown. in Fig. 4.

The hydraulic pump 32 may be of any suitable form and as shown is of thewell known Waterbury type which consists of a casing or housing in whicha rotatable cylinder barrel 86 is mounted upon a driving shaft 87. Asillustrated in Fig.-

8 the barrel 86 includes a plurality of cylinders 88 each having aport89 arranged to communicate in periodic succession with suction andpressure ports with which said pump is provided in the well mrown wayand which control the communication between said cylinders 88 and thepipes 31 and 34. Pistons 90 are slidably mounted in the cylinders 98 andare connectedby piston rods 91 with a swash plate 92 rotatably supportedin a tilting box 93 which is connected with `the driving shaft 87 bymeans of a universal joint 94 in the conventional manner. The tiltingbox 93 and awash plate 92 are adjustable to different angular positionsrelatively to the shaft 87 to vary the output .of the pump and thedirection of flow whereby the speed and direction of operation may beselectively changed, as will be pointed out more fully hereinafter. Thepump 32 .itself may be operated in any conventional manner, as by meansof an electric motor 94` connected with the driving shaft 84, of saidpump 32 for instance as shown in Fis. 1.

For the purpose of adjusting the position of the swash plate 92 andtilting box 93 of' the hydraulic pump 32, the tilting box 93 is providedwith a stub shaft 95 which ts into a rocking bearing 96 provided in acontrol shaft 97; the latter is vertically guidedin suitable guideways93 provided in the casing of the pump 32 as illustrated in Fig. 8. Inorder to facilitate the adjustment of the swash plate 92 andtilting=box93,

the actuation of the control shaft 97 is preferably effected by means ofa servo-motor 99, which, in the illustrated example, is mounted directlyupon the casing of the hydraulic pump 32, as illustrated in Fig. 8. Theservo-motor 99 may be of any conventional type, and as shown in thedrawings, comprises an upright cylinder in which a piston 100 isslidably mounted and connected with one end of the control shaft 97; thelatter projects into the cylinder of the servo-motor and is slid-J ablyguided in an adapter 101. lEhe piston 100 divides the servo motorcylinder into independent upper and lower chambers 102 and 103resignac-n tively, and itself is formed with longitudinal conduits 104and 105, the rst or' which opens to the upper chamber 102, while thesecond leads to the lower chamber 103. The conduits 104 and 105 areconnected by means of lateral branches with opposite end portions of avalve chamber 106 formed by a central bore in the piston 100, asillustrated in Fig. 8.

On its outer face, the piston 100 is cut away or reduced between itsends to form an annular passageway 107 between itself and the cylinderof the servo-motor 99, as best shown in Fig. 8; this annular passageway107 is connected by means oi a radial channel 108 with the valve chamberapproximately at the middle point of the latter. A sleeve 109 isconnected with and projects upwardly from thepiston 100 through asuitable stuiiing box 110 forming part of or se= cured to the cylinderof the servo-motor, the arrangement being such that said sleeve 109partalres of the vertical movement of the piston 100. A valve stem lllextends downwardly through the axial bore 112 of the sleeve 109 and atits lower end carries a pilot valve 113 slidably mounted in the valvechamber 105|. The pilot valve 113 is reduced at its central portion toprovide relatively enlarged end portions of heads 111 and 115 at itsopposite ends, which end portions slidably fit the valve chamber 106 ina fluid tight manner; in addition, the pilot valve 113 is provided withone or more longitudinally extending conduits l13a which establishcommunication between the opposite end portions of the valve chamber106.

Fluid under pressure for operating the servomotcr' 99 is supplied by alow pressure pump 116, which may be driven from the driving shaft 84 ofthe pump 32 by means of a sprocket chain or belt drive 117, as shown inFig. l. The pump 116 has its intake side connected by means of abranch-pipe 118 and a pipe 119 with the casing of the hydraulic -pump 32and has its outlet side connected by means of a branch pipe 120 andpipes 121`and 122 with a checkv valve 123, which in turn, is connectedby means of a pipe 124 with the annular passageway 107 of theservo-motor 99, the arrangement being such that in a certain position ofthe check valve 123. as will be' more fully explained hereinafter, lowpressure oil from' the pump 116 will be supplied to said annularpassageway 107 when the load on the servo-motor 99 is small. As clearlyshown in Fig. 3, the comxrminication between the pipes 122 and 124 iscontrolled by means of a valve 125 located in a chamber 126 of the checkvalve 123, saidvalve 125 being carried by a stem 126 and beingmaintained upon and returned to its seat by a relatively light spring128. The chamber 126 is connected by means o channels 129 withadditional chambers 130 and 131 respectively, said chambers 130 and 131in turn being connected by pipes 132 and 133 with the high pressure sideof the valve plate of Lacasse' the hydraulic pump 32, as shown inFig. 1. The communication between the chamber 130 and the pipe 132 andbetween the chamber 131 and 133 is controlled respectively by checkvalves 134 and 135 carried by-stems 136 and individually under theinuence of springs 137, as shown in Fig. 3. With this arrangement, aswill appear more `fully hereinafter, when vthe oil pressure increasesand thus causes an increased load on the servo-motor 99, high pressureoil is available from the high pressure side of the pump 32 for theoperation of said servo-motor.

The valve stem 111 of the servo-motor 99 is connected with an arm 138provided with a stop 139 extending between laterally spaced shoulders140 and 141 comprising parts of a stop bracket 142 carried by the sleeve109, as shown in Fig. 1; the arm 138 is carried by a vertically movablemember 143 slidably mounted in a bearing motor 99 and provided at itslower endfwith a roller 145. The roller 145 is'arranged in rollingengagement with a cam slide 146 and is main- ,tained in rolling contacttherewith by means of 148 mounted on the arm 138,whi1e the other ends ofsaid springs aresecured to projections 149 located upon the bearingbracket 144.

As shown in Fig. 2, the cam slide 146 comprises a lower .horizontalsection a and an intermediate recess or horizontal section b and anupper horizontal section c, the sections a and b being connectedby anlinclined section d and the sections b and c being connected by aninclined section e; the arrangement is such that the cam slide is ofsubstantially step-like form in which thehorizontal sections a, b and cyare located at progressively high levels. The cam slide 146 iS slidablymounted in a suitablev stationary horizontal guide 150 supported, for',instance, upon the casing of the hydraulic pump 32. For` the purpose ofadjustably and automatically determining the extent of the slidingmovements of thecam slide 146 in opposite directions, said cam slide isconnected with a screw threaded rod 151 forming a continuation of aslidable member or plunger 152 slidably mounted in a stationary bearing153 and including at its free end a screw threaded extension 154. Anexternally threaded collar 155 is threaded upon the rod 151 and acorresponding Acollar 156 is threaded upon the extension 154, saidcollars '155 and 156 constituting stops adapted to engage the oppositeends of the bearing 153 to thereby arrest the sliding movements of thecam slide 146 in opposite directions; Obviously, by shifting the collars155 and 156 on the rod 151 and extension 154 respectively, the extent ofthe reciprocating movement of the hydraulic pump 32, as shown inFlg. 2.The opposite ends of ,the cylinder 161 are independently connected bymeans of pipes 163'and 164 with a four-wayvalve 165 which in tum isconnected by means of a pipe'166 with the previously meng tioned pipel119'leading tothe casing ofthe hy- 115 draunc'pump 32 and by means ofa. pipeis'z with bracket 144 xed upon the casing of the servosprings 147connected at one end to projections relief valve 189 from which appe 196leads to cam slide 146 may be selectively adjusted; anyv the previouslymentioned pipe 121 and branch pipe 118 leading to the low pressure pump116.

`As shown in Fig. 7, the pipe 163 leads to a chamber 168 forming part ofthe valve 165, while the pipe 164 leads to a chamber 169 therein; thepipes 166 and 167 are connected respectively with chambers 170 and 171vof the valve 165, communication between said chambers and consequentlybetween the various pipes being 4controlled by slide valves 172 and 173slidably mounted in the casing of the valve 165 andcarried by a valverod 174 projecting exteriorly of the casing and terminating in a forkedmember 175 adapted for connection with a suitable operating member suchas a foot treadle which has been omitted from the disclosure. As shownin Figs. l and 2, a stud l'projects downwardly from the cam slide 146and is engaged by the ,opposed free ends of piston rods 177 and 178,which rods are slid z ably mounted in stulng boxes 179 located at oneend of cylinders 180 and 181 respectively; the rods 177 and 178 areconnected with pistons 182 and 183 winch are sliclably mounted in there= spective cylinders 180 and 181. Pipes 184 and 185 lead from theouter ends of the respective cylinders 180 and 181 and are connectedwith the previously mentioned branch pipe 120, which leads to the lowpressure pump 116. The inner end of the cylinder 180 is connected bymeans vof a pipe 186 with a pipe 164, while a similar pipe 187 connectsthe inner end of the cylinder 181 with the pipe 163. The pipe 185preferably is also connected by means'of a pipe 188 with a the casing ofthe hydraulic pump 32, as shown in Fig. 1.

In practice, during operative periods of the machine in which the novelfeatures are embodied, the hydraulic pump 32 will be continuouslyoperated by the motor 94 to rotate the barrel 36 and with it the swash-plate 92 and tilting box 93 with their associated. elements. With theparts illustrated in the neutral position in 8, in which the swashplateL 92 and tilting box 98 extend transversely at right angles to thedrivv ing shaft 87, no oil will be pumped by the pump 32 'and themechanism will accordingly remain stationary. When, however, the tiltingbox 93 and swash plate 92 are adjusted to inclined positio'ns indiagonal relation to the aforesaid driving shaft 87 in the manner to bemore fully set forth hereinafter, the pistons will be recipro cated inthe cylinders 88 and accordingly will pump oil or its equivalent throughthe pipes 3l. and x34." Under such conditions, with the tilting13u box93 and swash plate 92 inclined in one direction, oil from the one sideof the pump 32 passes through the by-pass relief valve 36 and shuttlevalve 30, and through the pipe 28 into the bore of the piston rod 20 andfrom thence through 135 suitable outlet ports into the one end chamberof the cylinder' A16. 'Ihe oil pressure thus created in. said chamberwill, by reacting against the aforesaid stationary piston, b e exertedYupon the right hand end of the cylinder 16 and accordingly will'movesaid cylinder, and with it the reciprocating table 15 toward theright in Fig; 1, for instance, at a relatively slofw speed.l At the sametime, the oil in the other end chamber of the' ..45

cylinder 1e will be forced through suitable ports 1 i and the bore ofthe piston 2l intoand through the pipe a3, by which' it is earned downtothd vback pressure valve 35. The oil pressure in the to the branchpipe 33a. With this arrangement, the action oi the back pressure valve35 serves to maintain a slight back pressure on the return side andthereby prevents jumping of the cylinder and the planer table or itsequivalent and steadies the travel of the latter in one direction. .esat this stage more oil is being pumped into the one chamber than ispassing out of the other cylinder chamber, due to differences indimensions of these chambers, the high pressure oil in the pipe 28 willbe eiiective in the chamber 29 of the shuttle valve 30 to close thevalve 37 thereof, and to open the co-operating valve 37a whereby thechamber 29a of said shuttle valve is brought into communication with thepipe 46 and the source of oil with which it communicates. With the partsin this position, a supply of oil accordingly passes from the oilexpansion box or other supply through the pipe 46 into the chamber 29aof such shuttle valve, which is in communication with the pipe 34leading to the pump 32, so that the deiiciency inthe amount of oilrequired for the cylinder chamber of larger dimensions is properlysupplied. To'cause the cylu inder 16 and table 15 to be moved on areturn stroke to the left in Fig. 1, the tilting box 93 `of the pump 32is adjusted to a reversed inclined position from that previouslyoccupied, so that oil under pressure now passes through the pipe 34,chamber 29a ofthe shuttle valve 30, branch pipe 33d into the check valve35. The pressure thus created operates said check valve 35 to permit theoil to pass through the pipe 33 to the bore oi the piston 21. Fromthence the oil passes into the other cylinder chamber and by reactingupon the stationary piston within said cylinder and acting upon the lefthand end of the cylinder 16 moves the latter, and with it the table 15toward the left in Fig. 1. Because of the relative dinerence in area ofsuch other chamber, this return movement of the vcylinder 16 and table15 may, for instance, be at a relatively high speed, so as to bringabout a quick return of the parts mentioned. During this operation, arelatively larger volume of oil may have to be displaced from thechamber at the right hand end of the cylinder 16, which is taken care ofin the following manner: The oil from the cylinder chamber in questionpasses through the bore of the piston 20 and is conducted therefrom bythe pipe 23 to the chamber 29 of the shuttle valve 39. During thisoperation, the valve 37a is closed, and the co-operating valve 37 isopened, so that the chamber 29 is in communication with the pipe 46whereby the excess oil is conducted to the oil reservoir or equivalentsupply.

In order to take care of any excessive overloads, which may develop inthe system, oninstance in case the planer table 15 or its equivalentshould stall against either one or the other end of f the machine, theby-pass valve 36 is provided,

said valve in effect constituting a relief valve which functions whenthe pressure has built up to a predetermined amount, in a condition for`instance as set forth above. Under such conditions oil from the pumpwill pass through the pipe 34 into this valve 36 and by moving the valve47 from its seat will flow through said by-pass valve 36 to the pipe 31and back to the pump 32. It will be noted that the valve 47 iscontrolled by the dash-pot arrangement 59-60 which not only preventschattering of this valve, but also serves to properly guide the same inits operative movements. In addition, the valve 47 includes a peripherallip 48 which assists in the opening or said valve and in maintaining itin an open position against the tension of the spring 51. The dash pots41-43 of the shuttle valve 30 likewise serve to prevent chattering ofthe valves 37 and 37a, which in many instances is severe enough to poundthe valves to pieces. The exible connections 42 between the valves 37and 37a respectively, and the plunger 4l of the aforesaid dash potsavoids any dimculties which otherwise might arise because ofmisalignment, and makes it unnecessary to provide extreme exactness inthe axial registry of these parts.

The mechanism so far described is controlledby means of the servo-motor99 and associated elements, which will now be described.

Oil for the operation of the servo-motor piston 100 is supplied by,thelow pressure pump 116 through the branch pipe 120, pipes 121, 122 to thecheck valve 123 and acts upon the valve 125 therein to permit said oilto ow into the chamber 126 and through the pipe 124 to the annularpassageway 107 of said servo-motor. Under cer tain conditions to be morefully referred to hereinafter, oil for the operation of said servo-motormay also be taken from the. high pressure side 1m oi' the pump 32through the pipes 132 and 133,

-which conduct said oil to the check valve 123 and by raising the valves134 and 135 permit said oil to pass into the chambers and 131, and

channels 129 to me pipe 124 and te the aforesaid m5 annular passageway107. With this arrangement, it is possible to use low pressure oil fromthe pump 116 when the load on the servo-motor 99 is small, and when theoil pressure increases and causes a greater load on thefservo-motor toE' utilize higher pressure oil from the high pressure side of the pumpitself. With the parts located as shown in Fig. l, the control mech isin a neutral position, in which theroller rests on the section or in therecess b of the cam Si slide 146. The setting of the cam slide 146,which controls the operation of the servo-motor 99 and consequently theadjustment of the hydraulic pump 32, is determined by operating thefour-way valve 165, the valve rod 174 of which may be manually operatedby any suitable means generally in the form of a foot pedal suitablyconnected to the forked member 175. By adjusting the valve 172 from theneutral position shown in Fig. 7 toward the left, pressure oil from them5 pipe 167 will pass through the chambers 171 and 163 to the pipe 163,and to the left hand end of the cylinder 161. The piston 160, and withit the stem 159 and cam'slide 146, is thus moved to the right in Figs. 1and 2 until the adjustable nut engages the one end of the ring 153. Asthis shifting of the cam slide 146 takes place, the roller 145 will rideup on the inclined section e to an extent determined by the position oithe nut 155 on the stem 151. The member 143 will be correspondinglyraised and will lift the arm 138, and bring about a corresponding upwardmovement of the valve stem 111 and accordingly raises the pilot valve1'14in the valve chamber 106, s@ that the conduit 105 is brought intocommunication with the radial channel 108 and consequently with theannular passageway 107. At this stage, oil under pressure willaccordingly pass to the chamber 103 beneath the piston 100 and will liftthe same to correspondingly raise the control shaft 97 and to therebyadjust the tilting box 93 and swash'plate 92 to an angular inclina.-tion with respect to the driving shaft 87. Unless the arm 138 is raisedextremely i'ast, the servo- 150 move almost in unison so-that the stop139 will not engage the shoulder 140; if however the arm 138 is liftedat an excessive speed the stop 139 will contact with the shoulder 140and thereby` 5 will prevent the pilot valve 113 -from' striking againstthe end of the sleeve 109in this direction of movement. The feeding'orequivalent speed of the table' 15 will thus be determined by the angularsetting of the swash plate 92. This speed obviously may be varied byshifting the nut 155 onthe stem 151 to permit the roller 145 to travelalong the inclined section e to a greater or lesser extent, the greatestspeed being attained when the travel of said roller 145 is such that itreaches the highest horizontal section c of the cam slide 146.Similarly, by shifting the valve rod 174 to Athe right in Fig. 7 asuicient distance to establish communication between the pipes 167 and164 through the chambers 171 and 169 of the four-way valve 165, oilunder pressure will be introducedv to the right hand end of the cylinder.161 through the pipe 164. This will cause the piston 160 to be moved tothe left in Fig. 1 and will correspondingly adjust the cam slide 14,6until the adjustable collar 156 engages the opposite end of the bearing153. Duringv these movements, the roller 145 will travel downwardlyalong-the inclined section d to the horizontal section a or to anintermediate point on said section d dependent upon the position of thecollar 156 on .the extension 154. As this happens, the member A143andarm 138 will be correspondingly moved downwardly and willcorrespondingly shift the .piot valve 113 downwardly in the valvechamber 106. If the downward movement of the arm 138 is extremely fastthe stop 139 will engage the shoulder 141 and thus will prevent thepilot 'valve 113 from contacting with the end of the Vcontrol shaft 97;otherwise the servo-motor piston and the pilot valve 113 will move-almost in unison in this direction also and the aforesaid contact willnot take place. The downward adjustment of the pilot valve 113 willbring the conduit 104 linto communication with the radial channel 108and accordingly will permit oil under pressure to pass into the'chamber102 above theA piston 100. The latter willltherefore be moved in adownward direction and will correspondingly 4adjust the control shaft 97to adjust the swash .plate 92 and tilting box 93 to an oppositely iniclined position relatively to the driving shaft 87. j This adjustment ofthe parts will cause the table ,15 or its equivalent to be operatedv ina return -rnovement It will be understood that the vertical movements ofthe piston 100 in the casing of the servo-motor 99 continues with eachsetting .of the pilot valve 113 until the inner ends of the lateralbranches of the conduits 104 and 105'over- .take and register with theheads 114 and 115 of the pilot valve'llS. From this it will be clearthat the extent to which the pilot valve 113 is shifted in the valvechamber 106 will determine the extent of movementpf the piston 100 andaccord- :ingly will predetermine the degree of adjustment of the tiltingbox 93 and swash plate 92 in one direction or the other relatively tothe driving shaft 87. 1 i

As the aforesaid upward movement of the piston 100 takes place, thepressure uid in the chamber 102 above said piston will' flow down-.wardly, through the conduit 104 to the lower end of the valve chamber106 from which said iiuid passes through a channel 97a, extendinglengthwise oi. the control shaft 97,-to the interior oi' the casing.. ofthe pump ,32. Similarly asi-.the piston -a supply of oil at relativelyhigher pressure to Same Way.

. left in Figs. 5 and 6. in a return stroke. -teedingpr other operativestroke, in which the 100 moves downwardly, the pressure fluid in thechamber 103 beneath said piston, will be forced up through the conduit105 to the upper end of the valve chamber 106; from this point saidfluid flows downwardly through the channels 113a of the pilot valvell3and through the aforesaid '80 channell 97a to the interior of thecasing of the pump 32.

If at any time during the operation set forth above, the oil` pressureincreases, for instance, .85

4when actual work is being performed by the reach the servo-motorthrough the pipe 124 and 95 to operate the same in the intendedvmanner.Which one of the valves 134.01' 135 is operated under .these conditionswill be determined by the direction in which the servo-motor -piston 100is being actuated at the time.

For the purpose of automatically restoring the cam slide 146 to theneutral position shown in Figi, and for maintaining it therein, thecentering cylinders 180 and 181, and their associated elements, areprovided. The arrangement `is lan adjustable high speed return strokeand for positive centralization in the neutral position. In practice, ithas been found that in some invstances the cutting or other operativestroke con.-

sists in part of what might be termed an ineifective initial stroke anda continuing effective stroke, under which conditions it becomes de- 325sirable te have part of said strokeoperate at a relatively higher speedin order to bring the parts to the actual operative position as quickiyas possible. I A' An example of an arrangement whereby these 1g@ resultsmay be accomplished is shown in Figs. 5 and 6. As illustrated in thesefigures the machine, in the main, is the same as'th'at previouslydescribed and operates in approximately the Instead of the adjustablenut 155 and collar 156 andthe co-operating fixed stops represented bythe opposite end of the bearing 153 Iincluded in the machine rstdescribed, an ad- -b. The stop 155e is located in the path of the cam's1ide 146 and is directly engaged thereby when said cam slide 146 ismoved toward the 145 0n the piston 160, and with it the piston rod 159and cam slide 146, moves towardthe right in Figs.

5 and 6. said cam slide 146 engages an adjustable 15 stop 1561i. r.ihelatter consists of a rod slidably mounted in the stufling box 153b of astationary cylinder 153e suitably supported in the machine, said stoprod 156a being connected with a piston 152e slidably mounted in saidcylinder 153e as shown in Fig. 5. PEhe piston 152e is hollow andisarranged to reciprocate relatively to a head 152i located interlorly ofsaid piston, and carried by a rod 152e which projects through an opening152d formed in the removable end memher 152e of said piston 152a asillustrated in Fig. 5. The rod 152e is adjustable lengthwise of thecylinder 153e to vary the position of said head 1525 which constitutes astop to limit the movement oi' the piston 152e toward the left in Fig.5, as will appear more fully hereinafter; for this purpose the rod 152eis in threaded engagement with the removable member 15311 of thecylinder 153e and is xed in an adjusted position, for instance, by locknuts 153e; to protect the latter against unintentionalinisadjustmenu'said nuts and the outer end of the rod 152e may normally:be covered by a protecting cap 153i which is screwthreaded upon a bossprojecting from' the member 153d as shown in Fig. 5. The cylinder 153eis provided at its opposite ends with ports 191 and 192 respectively,from the rst of which a pipe 193 leads to the pipe 119, which connectswith the branch pipe 118 of the pump 116 and with the casing of the pump32, so that said pipe 193 may be said to be always open to the exhaust;the second port 192 is connected by means oi a pipe 194 which leads tothe casing of a control valve 195 as illustrated in Fig. 6. The valvepip-es 119 and 121 respectively, and accordingly place the chambers oithe valve 195 which correspond to the chambers 170 and 171 of the valve165, in communication with the hydraulic pump 32 and the pump 116, asillustrated diagrammatically in Fig. 6. The internal construction oi thevalve 195 includes slide valves similar to the slide valves 112 'and 1TBof the valve 165 and similarly adjustable by means of a valve rod 174eprovided at its free end with a forked member 17511 adapted iorconnection with a suitable operating member such as a foot treadle as inthe case of the valve 165.

With the arrangement shown in Figs. 5 and 6, and assuming that thepiston 152a occupies the extreme left hand position shown in saiddgures, the cam slide 146 will be shiftable to the right only to aslight extent until arrested by engagement with the stop rod 1561i. Thiswill cause only a slight upward travel of the roller 145 on the-sectione of the cam slide 146 and thus will bring about an operation of theservo-motor 99 which produces only a slight angular displacement of thetilting box 93 and swash plate 92 of the hydraulic pump 32; as a result,the operation of the parts will be such the table will develop anoperative movement at relatively slow speed. The left hand position ofthe stop rod 156s and the speed of the operative movement of the partsmay be varied by adjusting the nuts 153s on the rod 152e, this willcorrespondingly shift the head 152s which arrests the movement of thepiston 152s to the left and thus determines the left hand position ofthe stop rod 156a and the extent of right hand movement of the cam slide146.

-When it is desired to operate the table 15 or its equivalent at amaximum speed the valve rod 174a is shifted to operate .the valve 195 insuch a manner that the pipe line 194 is brought into communication withthe pipe 196 and pipes 166 and 119, and accordingly is open totheexhaust. This releases the pressure in the cylinder 153e which iseffective on the right hand end of the piston 152a therein. This willallow the pressure exerted on the piston 160 toward the right and theresulting movement of the cam slide 146 to shift the stop rod 156a tothe right until the piston 152B is arrested at the right hand end of thecylinder 153e in Figs. 5 and 6. The cam slide 146 will under suchconditions be capable of moving to the right in Fig. 5. to a maximumextent before being arrested by the stop rod 156a with the result thatthe roller 145 will travel upwardly on the section e of the cam slide tothe top thereof. The servo-motor 99 will consequently be operated in amanner to bring about a greater angular displacement of the tilting box93 and swash plate 92 and the output of the pump 32 will be increased sothat in the illustrated example the speed of operation of the table 15correspondingly increased.

As previously stated, by shifting the location of the head 1525 throughthe medium of the rod 152e and nuts 153e the point at which the movementof the piston 15241 toward the left in Fig. 5 is arrested by the stoprod 156e, may be varied. It will be understood that the piston 152a ismoved toward the left and maintained in its iinal left hand position bypressure uid passing into the cylinder 153c through the port 192 from.the pipe 194 as a result oi a proper manipulation oi the valve 195. Withthe aforesaid arrangement the cam slide 146 will be pushed to the rightin Figs.`

5 and 6 until it engages the stop rod 156B and may be held in thisadjustment as long as desired by the operator, after which said camslide 146 may be permitted to shift to a iull right position by theoperation of the valve 195 as set forth. The cam slide 146 may bereturned toward the left to an intermediate position by suitablymanipulating the valve 195 to introduce pressure uid to the right handend of the cylinder 156e through thepipe 194. It is thus possible toprovide for an intermediate speed between zero and the maximum speedyobtainable when the roller 145 reaches the top of the cam slide 146.

lin the illustrated examples so far described, the table 15 is operatedby a plunger type hydraulic motor indicated by the cylinder 16, piston17 and associated elements. It will be understood that the operation ofthe table 15 may be accomplished by means of a conventional mrdraulicmotor of the rotating type and arranged to drive the table through asuitable set of spur gears and a rack as is usual, for instance, in

planer construction, said motor' being connected' with the pump 32 inthe usual way. In such installations, the back pressure valve 35 and theshuttle valve 30 may be omitted as the high speed return may be secureddirectly throughthe control of the hydraulic pump 32..V

The novel features, when embodied in reciprocating machine tools such asplanets, milling machines and the like provide deiinite and specializedcontrol for such machines and bring about operations of maximumeiilciency. With the arrangements set forth the speed of operation ofthe machine tool may be varied and adjusted to efilciently meet therequirements of any type of work Within the operative range of themachine.

Various changes in the specific forms shown and described may be madewithin the scope of the claims without departing from the spirit of theinvention.

I claim:

1. Controlling mechanism for a variable ow, reversible pump comprising aservo-motor for adjusting saidv pump to vary the operation thereof,setting mechanism for controlling the operation of said servo-motor, areciprocating cam slide for variably actuating said setting mechanism, apressure actuated piston whereby 'said cam slide is operated, anadjustable stop for engaging said cam slide to arrest its movements inone direction, and a pressure actuated adjustable stop for engaging saidcam slide to arrest its movementsA in the opposite direction.

2. Controlling mechanism for a variable flow, reversible pump comprisinga servo-motor for adju'sting said pump to vary the operation thereof,setting mechanism for controlling the operation of said servo-motor, areciprocating cam slide for variably actuating said setting mechanism, apressure actuated piston whereby said cam slide is operated, anadjustable stop for engaging said cam slide to arrest its movements inone direction, I

rest its movementsin the opposite direction, andl adjustable meanswhereby the movements of said piston and stop rod in one direction arearrested.

3. Controlling mechanism for a variable flow, reversible pu'mpcomprising a servo-motor for adjusting said pum'p to vary the operationthereof, setting mechanism for controlling the operation of saidservo-motor, a reciprocating cam slide for variably actuating saidsetting mechanism, a pressure actuated piston whereby said cam slide isoperated, an adjustable stop for engaging said cam slide to arrest itsmovements in one direction, a stationary cylinder connected with asource of pressure, a hollow piston slidable in said cylinder, a stoprod connected with said piston and constituting an adjustable stop forengaging said cam slide to arrest its movements in the oppositedirection, a head located within said piston for determining the extentof movement of the piston and stop rod in one direction, and anadjustable rod carrying said head for selectively Varving the positionof the latter. Y

ARTHUR L. ELLIS.

